In the manufacture of semiconductor devices, it is necessary that such devices be tested at the wafer level to evaluate their functionality. The process in which die in a wafer are tested is commonly referred to as “wafer sort.” Testing and determining design flaws at the die level offers several advantages. First, it allows designers to evaluate the functionality of new devices during development.
Increasing packaging costs also make wafer sorting a viable cost saver, in that reliability of each die on a wafer may be tested before incurring the higher costs of packaging. Measuring reliability also allows the performance of the production process to be evaluated and production consistency rated, such as for example by “bin switching” whereby the performance of a wafer is downgraded because that wafer's performance did not meet the expected criteria.
The process of die-testing and wafer sort may be carried out with a wafer probe card. A probe card is an interface between an electronic test system and a semiconductor wafer. Typically the probe card is mechanically docked to a prober and electrically connected to a tester to provide an electrical path between the test system and the circuits on the wafer, thereby permitting the testing and validation of the circuits at the wafer level, usually before they are diced and packaged.
Periodically, sort probe over current events may result in probe head damage due to melted or recessed probes. The damaged probes must be repaired or removed to prevent improper binning. In severe instances, the entire probe head, which may be valued at several tens of thousands of dollars, will need to be discarded as the damage is beyond repair. In cases where repair is viable, however, the repair process requires specially trained technicians to manually manipulate or pluck probes working under a microscope. Thus, the repair process is labor intensive and a production limiter as probe cards scale to tighter pitches and higher probe counts.